A new simulation has shed light on what happens to your body when you fast for 36 hours, showing how this period of abstaining from food can trigger major changes.
Historically, humans often went without food due to environmental conditions, reliance on harvests, or financial constraints. Dr. Valter Longo, a longevity researcher at the University of Southern California, explained that people were “forced to fast” in the past, whereas today, food is available almost everywhere.
Dr. Vicki Catenacci, a nutrition researcher at the University of Colorado, added that modern eating patterns have shifted significantly, with most people eating across an average 14-hour period each day.
What happens in your body during a 36-hour fast
According to a simulation by YouTube channel Wellness Wise, fasting triggers several processes in the body:
- After 4 hours: Insulin levels drop, and the body begins burning stored sugar.
- After 8 hours: Blood sugar declines as glycogen, the primary storage form of glucose, is used for energy.
- After 12 hours: Fat burning begins, entering a state called ketosis, where the body relies on fat instead of carbohydrates for fuel.
- Within 16 hours: Autophagy starts, breaking down damaged cells and toxins.
- After 24 hours: Cellular repair increases, inflammation drops, and insulin sensitivity improves.
- At 30 hours: Growth hormone spikes, preserving muscle and promoting fat loss.
- By 36 hours: Maximum autophagy occurs, dead cells are cleared, tissues regenerate, and metabolism reaches its peak—completing a “full body reset.”
What experts say
Associate Professor Adam Collins of the University of Surrey noted that stricter fasting leads to faster fat burning compared to carbs, though much of the research is animal-based. He cautioned that the effects of a 36-hour fast once a week in humans are not fully understood.
Professor James Bett, a metabolic physiology specialist at the University of Bath, also emphasized that while fasting may have benefits, the evidence in humans is limited. He added that low energy during fasting can reduce physical activity, and fasting beyond 24 hours may even prompt the body to store fat as a survival response, according to Johns Hopkins Medicine.
While fasting can kickstart processes like autophagy and cellular repair, experts suggest that regular exercise might be a safer and more sustainable way to maintain health.
